This invention relates to touch screen sensors and in particular to the electrode pattern formed on the border of the resistive layer of the touch screen panel.
Touch screen panels generally comprise an insulative (e.g. glass) substrate and resistive layer disposed on the insulative substrate. A pattern of conductive electrodes are then formed on the edges of the resistive layer. The conductive electrodes form orthogonal electric fields in the X and Y direction across the resistive layer. Contact of a finger or stylus on the panel then causes the generation of a signal that is representative of the x and y coordinates of the location of the finger or stylus with respect to the substrate. In this way, the associated touch panel circuitry can ascertain where the touch occurred on the substrate.
Typically, a computer program generates an option to the user (e.g. xe2x80x9cpress here for xe2x80x98yesxe2x80x99 and press here for xe2x80x98noxe2x80x99xe2x80x9d) on a monitor underneath the touch screen panel and the conductive electrode pattern assists in detecting which option the user chose when the touch screen panel was touched by the user.
There have been numerous attempts to linearize the orthogonal fields across the resistive layer in order to locate the exact position of a touch on the touch screen and to increase the usable area of the touch screen.
In general, however, linearization efforts come at a cost: namely, the size of the electrode pattern, because linearization can be optimized by increasing the number of rows of electrode segments, or the complexity by producing the insulated segments in the electrode pattern. These efforts, in turn, increase the size, and in particular the width of the electrode pattern along the border of the touch screen panel thereby reducing the usable touch screen space, or increase the manufacturing complexity and cost.
Three major factors are used to evaluate the electrode configuration. The first and most obvious factor is the linear response. The second factor is the complexity in manufacturing these electrode patterns, which indicates the cost factor. The third factor is the width of the electrode patterns, which also. indicates the cost factor. These electrodes can occupy considerable space along the edge of the touch sensor. Given today""s display technology, the size of a display frame can be reduced to save space. Therefore, a larger electrode pattern will partially invade the display""s viewable area, rendering the touch sensor unusable.
None of the prior art electrode pattern configurations satisfactorily resolve all three factors and must sacrifice either linearity, narrow width or simplicity.
See U.S. Pat. No. 4,822,957 and U.S. Pat. No. 4,371,746 incorporated herein by this reference. Both U.S. Pat. No. 4,822,957, which is currently used in Elo Touch""s 5 wire resistive touch panel, and U.S. Pat. No. 4,371,746, which is currently used in MicroTouch""s capacitive touch panel, exhibit considerable hooks of equipotential lines near the conductive segments. Furthermore, Elo""s electrode pattern is composed of conductors and insulators which are produced in two separate processes. The MicroTouch electrode pattern occupies a considerable amount of space.
It is therefore an object of this invention to provide a touch panel with an improved linear response and minimum border width edge electrode pattern.
It is a further object of this invention to provide such a touch panel at a low cost and using manufacturing techniques which result in a higher yield.
It is a further object of this invention to provide such a touch screen panel which is simple to manufacture and uses simpler electrode configurations.
This invention results from the realization that the linearity of a touch screen panel can be improved at the same time the size and especially the width of the electrode pattern is reduced not by complex electrode configurations but instead by a continuous repeating pattern of rows of spaced electrode conductive segments wherein every row including the outermost row has at least two conductive segments facing three conductive segments in the next adjacent inner row. In this way, the number of gaps is increased but each gap can be made smaller and the rows placed closer together resulting in improved linearity and a smaller size electrode pattern both of which increases the usable touch screen space.
A touch screen panel comprising an insulative substrate, a resistive layer on the insulative substrate, and a plurality of spaced conductive segments on the resistive layer along the border thereof, the conductive segments disposed in rows, every row having at least two segments each facing at least a portion of three segments in an adjacent row for improving the linearity of the touch screen panel and at the same time reducing the space occupied by the conductive segments on the touch screen panel.
Preferably, at least two segments of each row face each one complete segment and portions of two other segments in an adjacent row. Usually, a majority of the conductive segments in a row are of equal length.
There may be K total rows and 2(Kxe2x88x92L+2)+1 segments in each row with L being the row number and L=1 denoting the innermost row on the panel. K should be at least two so that there are at least two rows.
In many embodiments, there is a center conductive segment which extends across the rows of conductive segments. Usually, there is a center segment on each side of the panel. Also, a back shield layer is usually disposed on the substrate opposite the resistive layer. A conductive electrode may be disposed circumferentially on the back shield layer.
For resistive touch screen panels, a flexible layer is spaced from the resistive layer, and a plurality of insulated spacer elements are disposed between the flexible layer and the resistive layer for maintaining separation between the flexible layer and the resistive layer.
A plurality of electrode leads are connected to different conductive segments to generate an electrical field across the resistive layer. In one embodiment, the electrical leads are wires. In another embodiment, the electrical leads are lands deposited on a dielectric layer disposed on the resistive layer.